Study On District Cooling Of Cylinder Liner And Floating Liner Friction

With the increasing requirement of environment and energy,the design and development of diesel engine tend to high power density.With the continuous improvement of the strengthening index,the friction power consumption of diesel engine increases obviously and the wear intensifies.Cylinder liner-piston ring assembly is one of the most typical friction pairs of diesel engine,and the friction loss accounts for about 50%of the mechanical loss of diesel engine.It is of great significance to study the friction and wear law of the cylinder liner-piston ring assembly in order to save energy,reduce consumption,improve efficiency and prolong the service life of diesel engine.In this paper,the liner cooling water jacket with district cooling:function and the friction test bench of cylinder liner-piston ring assembly based on floating liner method are designed.The influence of three kinds of cooling methods on the friction and frictional work of the cylinder liner-piston ring assembly under different working conditions was obtained.The three-dimensional transient lubrication mathematical model of tibhe jack-piston ring group was established to explore the influence of zone cooling on the minimum oil film thickness,fluid and asperity of the cylinder liner-piston ring assembly,and the following results were obtained:(1)The friction test bench of cylinder liner-piston ring group based on floating cylinder liner method is designed,which can realize on-line measurement of friction force under fired condition of diesel engine.The parameters of various working conditions can be adjusted,and the measured friction data is stable and reliable.The cooling water jacket with partial cooling function is designed.The water jacket has two separate cooling water Chanbers,which can control the axial temperature field distribution of the cylinder liner,thus adjust the viscosity of lubricating oil in the corresponding region and optimize the lubrication condition of the cylinder liner at different positions.(2)Under different speeds,loads and lubricating oils,the average friction power of cylinder liner-piston ring assembly corresponding to partial cooling method A(upper cooling water chamber with 10? cooling water,lower cooling water chamber with 10? cooling water),B(upper cooling water chamber with 10oC cooling water,lower cooling water chamber with 40? cooling water),C(upper cooling water chamber with 10? cooling water,lower cooling water chanber with 70? cooling water)is calculated.The average friction power decreases in turn.(3)Comparing the district cooling method C with the partial cooling method A,the higher the speed of diesel engine is,the more obvious the decrease of average friction power is.The decrease of average friction power is 14.7%at 2200 r/nin;the increase of diesel engine load has little effect on the decrease of average friction power;the higher the viscosity of lubricating oil,the more obvious the decrease of average friction power is5 and the decrease of average friction power is 13.6%when using SN5W.40 lubricating oil.(4)The minimum oil film thickness,fluid friction force and friction power,asperity friction force and friction power of cylinder liner-piston ring assembly were obtained through simulation calculation.Compared with partial cooling method C and partial cooling method A,the minimum oil film thickness in the middle part of the stroke is reduced,and the friction power loss of fluid is obviously reduced,while the friction work loss of asperity is basically unaffected.